limiter: fix missing route patch when only configuring json_body match

[believening]

import from: https://github.com/slime-io/slime/pull/427. https://github.com/slime-io/slime/pull/468

gogoproto 对长度为零的非空切片执行序列化时，会保留字段，golang proto 不会，导致生成 json-body match 失败。